#back {
  width: 100%;
  min-height: 100vh;
  background-color: #efccff;
  background-image: radial-gradient(closest-side, #19b6ff, rgba(0, 0, 0, 0)), radial-gradient(closest-side, #ff9999, rgba(0, 0, 0, 0)), radial-gradient(closest-side, #f07b3f, rgba(0, 0, 0, 0)), radial-gradient(closest-side, #d59bf6, rgba(0, 0, 0, 0)), radial-gradient(closest-side, #ffb400, rgba(0, 0, 0, 0));
  background-size: 130vmax 130vmax,
    80vmax 80vmax,
    90vmax 90vmax,
    120vmax 120vmax,
    90vmax 90vmax;
  background-position: -80vmax -80vmax, 60vmax -30vmax, -30vmax -10vmax, 20vmax 80vmax, 10vmax 10vmax;
  background-repeat: no-repeat;
  position: fixed;
  z-index: -1;
  animation: 10s movement linear infinite;
  backdrop-filter: blur(10px);
}
#back::after {
  content: '';
  display: block;
  position: fixed;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
}
@keyframes movement {
  0% {
    background-size: 130vmax 130vmax,
      80vmax 80vmax,
      90vmax 90vmax,
      120vmax 120vmax,
      90vmax 90vmax;
    background-position: -80vmax -80vmax, 60vmax -30vmax, -30vmax -10vmax, 20vmax 80vmax, 10vmax 10vmax;
  }
  25% {
    background-size: 110vmax 110vmax,
      90vmax 90vmax,
      100vmax 100vmax,
      90vmax 90vmax,
      60vmax 60vmax;
    background-position: -60vmax -90vmax, 50vmax -40vmax, 0vmax -20vmax, -20vmax 50vmax, 40vmax 60vmax;
  }
  75% {
    background-size: 90vmax 90vmax,
      90vmax 90vmax,
      100vmax 100vmax,
      90vmax 90vmax,
      70vmax 70vmax;
    background-position: -50vmax -40vmax, 50vmax -30vmax, 20vmax 0vmax, -10vmax 10vmax, 40vmax 60vmax;
  }
  100% {
    background-size: 130vmax 130vmax,
      80vmax 80vmax,
      90vmax 90vmax,
      120vmax 120vmax,
      90vmax 90vmax;
    background-position: -80vmax -80vmax, 60vmax -30vmax, -30vmax -10vmax, 20vmax 80vmax, 10vmax 10vmax;
  }
}
